Kevin Blackwell has described the decision to appoint Mike Dean to referee Monday's Championship play-off final between ­Sheffield United and Burnley as "absolutely inexplicable". The United manager was deeply unhappy with Dean after he dismissed Matthew Kilgallon at Hillsborough last October and has severely criticised the Professional Game Match Officials for asking the Premier League referee to take charge of a game that could put him in an "embarrassing position".

Blackwell said he gave Dean an ­"exceptionally low" mark following his performance in the Sheffield derby and believes United supporters will make life uncomfortable for the referee at ­Wembley because of the injustice they still feel from that day. Kilgallon was sent off for raising a boot into the ribs of Sean McAllister and Blackwell later described Dean's decision to brandish a straight red card in a fixture that United lost 1–0 as "pathetic".

"I cannot believe they have appointed Mike Dean when his last game was at Hillsborough when he sent off Matthew Kilgallon," said Blackwell, who says that he is still awaiting a response from the PGMO after he voiced his concerns. "I marked him exceptionally low and all of a sudden who's in the final? Mike Dean. Everyone knows about the controversy caused by the sending off of Matthew Kilgallon and it was talked about in football in great depth. I just find it absolutely inexplicable.

"I've spoken to the people that matter, who do the appointments, because it's not fair on Mike Dean, Kevin Blackwell or Sheffield United football club, because our last meeting was less than amicable. Now he suddenly turns up for our biggest game and the biggest club game in the world. I want to know why the stupidity of people?

"We're going to go to Wembley with 40,000 Sheffield United fans knowing his last performance cost us a result at Hillsborough screaming down his neck. That's not fair on Mike Dean or me. We all have off days, that's not the issue. The issue is they're putting Mike Dean under pressure in this particular game. They have created a situation which they need not have created. Now everyone will be watching Mike Dean to see if he makes any controversial decisions. Is that right?

"Can you imagine what will happen if Mike Dean makes a cock-up on Monday after what happened at Hillsborough. How stupid is that? I'm very, very angry about people who run the game not using their common sense and putting Mike Dean in what could be a very embarrassing position. I think he's a good referee and I respect him. The problem is that his last game was poor. That's not just coming from me, that's coming from a lot of people in the game."

Although Dean was removed from the 2006 FA Cup final because of ­concerns that living in the Wirral, close to ­Liverpool, would compromise him when Rafael Benítez's side took on West Ham United, there is no chance of the PGMO replacing him for Monday's fixture. A spokesperson for the PGMO said: "Mike Dean is top of the assessment marks in the select group of referees and the person who finishes top is traditionally selected for the play-off final."

Blackwell's decision to air his frustration about Dean's appointment might well be seen as an attempt to apply some psychological pressure on the referee. Last month Sir Alex Ferguson, who is prone to a comment or two about officials before significant matches, queried whether David Moyes's decision to publicly question the appointment of Mike Riley for the FA Cup semi-final might have influenced the official to ignore Manchester United's late claims for a penalty in that game.